Liquid spills are common and may be small or large in scale. Small spills, such as those involving personal activities such as cooking or attending to the maintenance of a motor vehicle may be cleaned up with cloth or paper. Sawdust, animal litter, or another absorbent material may be used to solidify small spills prior to removal. Larger spills resulting from accidents involving the transport of bulk quantities of liquids, discharge of operating fluids from large machines, or spent drilling fluids may require special vacuum equipment, treatment with an absorbent material, or another means for solidifying the liquid before it can be removed and lawfully disposed.
To clean up a spilled liquid, an absorbent solid material is placed on the liquid and the material absorbs the liquid. An absorbent solid material may also be placed in anticipation of liquid contact. Solids employed in this capacity have typically included cloth, paper, sawdust, and certain minerals in granular or powdered form. Organic materials such as corn, wheat, and walnut shells have also been utilized for liquid absorption, particularly for animal litter. Naturally-occurring substances such as sand, pulverized ceramics, clay, expanded perlite, and diatomaceous earth (DE) may be employed, especially for large scale spills. The absorbent solid material is gathered and disposed after it has absorbed a satisfactory amount of the liquid.
The effectiveness of an absorbent material is measured by its capacity to absorb liquid, known as its absorbent capacity or absorbency. As used herein, the term “absorbency” describes the amount of liquid absorbed by unit mass of absorbent. A higher absorbency may result in better efficacy and lower aggregate cost in terms of transport and disposal. Low density absorbents are desirable because they may be, in some cases, easier and cheaper per unit volume to transport, to handle for use, and to dispose following use. Another desirable attribute of absorbent materials is the ability to self-solidify or agglomerate to form clumps after being wetted. Agglomeration of the material forms an integral mass that holds the absorbed liquid and has enough strength to be removed from the spill site or separated from the unsoiled absorbent. For example, some animal litters agglomerate or self-clump after absorbing urine. The resultant clumps may then be easily removed from the litter box, thus leaving the unsoiled animal litter behind. The integrity of the clump can be quantified as the clump strength. As used herein, the term “clump strength” is the percent value of the clump's initial mass that is retained after the clump is mechanically disturbed, moved, or agitated.
As previously described, an ideal absorbent material would possess high absorbency, low density, and good agglomeration to form a strong clump. While low density is desirable in most applications, too low of a density can be problematic. For example, a very low density absorbent, such as expanded perlite, can be very dusty and can be dispersed easily by a light breeze or air flow. Low density absorbents, such as perlite or compositions comprising perlite, can also be undesirable for use as animal litters, as the animal may inadvertently disperse or kick the litter out of a litter box during use. Further animal litters that are dusty are undesirable because animals and their owners may inhale airborne animal litter particles when either using or maintaining the litter box, respectively. Particle inhalation is undesirable. Crystalline silica (e.g, quartz, cristobalite, tridymite) is an example of a material that is undesirable to inhale. Minimizing exposure to crystalline silica is preferred. Compositions containing high levels of arsenic (As) are also undesirable in case a person or animal were to ingest or solubilize (e.g. via wetting such as licking) the absorbent.
Slacking or mudding is a well-known problem for low quality absorbents. Slacking refers to the tendency of an absorbent to disintegrate after contact with water thereby decreasing absorbent effectiveness. Another problem associated with currently available absorbents is density. Sodium bentonite is an effective absorbent due to its high absorbency and ability to absorb water, but it is less than ideal due to its high density. Sodium bentonite is primarily comprised of sodium montmorillonite, a type of smectite clay. Diatomaceous earth, also known as diatomite and kieseighur, is of low density but has a lower absorbency than sodium bentonite.
Accordingly, there is a need for a composition with superior absorbency, low density, low dustiness, and improved stability in terms of high clump strength and resistance to slacking.
Commonly used absorbents are clay-based materials, including both clumping and non-clumping clays such as sodium bentonite (for example, Wyo-Ben™ Big Horn® clay) and calcium bentonite (for example, EP Minerals® (“EPM”) Blue Ribbon clay), respectively. Hectorite is another clumping clay. Clumping materials, such as sodium bentonite and hectorite, swell or change in particle volume as a function of the amount of liquid, such as water, absorbed, a phenomenon related to the crystal structure, composition, and surface properties of the material. Sodium bentonite has a much higher absorbency by unit mass than calcium bentonite (3˜5 x). Sodium bentonite is used for its high absorption and good agglomeration despite its high density. While calcium bentonites generally do not swell sufficiently to be effective as clumping agents in, for example, animal litter or the like they can be modified to behave like sodium bentonites through an ion-exchange process. These sodium-beneficiated calcium bentonites are also sometimes called sodium-activated bentonites. For the purposes of this invention, sodium bentonite is defined to include both conventional sodium bentonites and sodium-beneficiated calcium bentonites. Other currently available absorbents do not have high absorbencies and some become slacked after being wetted. Examples of non-clay materials include DE and zeolites. Diatomaceous earth is a siliceous rock comprised of skeletal remains of diatoms. Zeolites are naturally occurring or synthetic porous aluminosilicate materials. Non-clumping materials do not naturally form clumps with high clump strength. As used herein, “clumping” will refer to materials that, when wetted, form a clump that demonstrates high clump strength or integrity. Similarly, “non-clumping” will refer to materials that do not self-clump or materials that self-clump but demonstrate poor clump strength. Poor clump strength is defined as below about 75%.
Desirable animal litter characteristics include high absorbency, an ability to clump, low density, low dustiness, low tracking, low slacking, and odor control. Some animal litters include fragrances, deodorants, clumping agents, and foaming agents.